Essays / A persuasive essay on global warming: need help on the intro to my essay [3]

I am not the best at writing papers, especially when it comes to the introduction. I have to write a persuasive essay on global warming. Can anyone give me an idea on how to do this? I just need a sentence or two to start my brain, I can usually go from there. I need to persuade the reader that humans do in fact have an impact on global warming.

Thanks